Pressure sensitive adhesives natural rubber-based

Natural-rubber-based pressure-sensitive adhesives can be cured by standard mbber curatives, eg, sulfur plus an accelerator (see Rubber, natural) ... 

Fujita M., Kajiyama M., Takemura A., Ono H., Mizumachi H., Hayashi S., Effects of miscibihty on probe tack of natural-rubber-based pressure-sensitive adhesives, J. Appl. Polym. ScL, 70(4), 1998, 771-776. 

The conventional method for characterizing natural rubber, Mooney viscosity, is not sensitive enough to be used to obtain the necessary information for natural rubber-based pressure-sensitive adhesive characterization. The RDS generates better information than the Mooney viscometer. 

Pressure sensitive adhesive tapes are used for holding and anchoring lead wires to the outer wrap of transformer coils, capacitor wrapping, protection of leads and coils, and other similar applications. Adhesive transfer films are used to hold insulating material in position. Natural rubber based pressure sensitive adhesives have poor solvent resisitance unless they are cross-linked. Many modifications are possible. Synthetic rubber has better stability than natural rubber and better solvent and ozone resistance. Acrylic pressure sensitive adhesives have the best balance of properties. They maintain their... 

There have been very few studies reported on the viscoelastic properties of rubber-resin pressure sensitive adhesive systems. In 1973, M. Sherriff and co-workers (1) reported on the effect of adding poly (j3-pinene) resin to natural rubber. Based on a G master curve, they showed that the resin shifted the entry to the transition zone to a lower frequency and reduced the modulus in the rubbery plateau. G. Kraus and K.W. Rollman (2) reported in 1977 on their study of resins blended with styrene-isoprene-styrene block copolymers. They showed that the addition of a resin increased the glass transition temperature of the rubbery mid-block and decreased the plateau modulus. Accordingly, a satisfactory tackifying resin should produce these changes. 

In Figure 8, the viscoelastic properties of natural rubber latex (Hartex 103 from Firestone Co.) and milled smoked sheet natural rubber were examined. Both natural rubbers have tan 8 peak maximum temperature at -58°C. However, the latex has higher room-temperature modulus than the milled natural rubber. Natural rubber latex based pressure-sensitive adhesives offer an advantage over solvent-based systems (milled smoked sheet) because of the molecular-weight difference between the two systems. The high-molecular-weight portion of natural rubber is insoluble in solvent and therefore cannot be used in solvent-based adhesives. Natural... 

Oxygen in the atmosphere generally attacks polymers. In many cases, the rate of attack, even at ambient temperatures, necessitates the use of stabilizing additives. Examples of adhesives that normally contain antioxidants are hot-melts, those based on natural and synthetic rubbers, and pressure-sensitive adhesives. 

Natural rubber was the first polymer base for the early pressure sensitive adhesives. Their origin may be traced to the early medical plasters formulated in... 

Among the different pressure sensitive adhesives, acrylates are unique because they are one of the few materials that can be synthesized to be inherently tacky. Indeed, polyvinylethers, some amorphous polyolefins, and some ethylene-vinyl acetate copolymers are the only other polymers that share this unique property. Because of the access to a wide range of commercial monomers, their relatively low cost, and their ease of polymerization, acrylates have become the dominant single component pressure sensitive adhesive materials used in the industry. Other PSAs, such as those based on natural rubber or synthetic block copolymers with rubbery midblock require compounding of the elastomer with low molecular weight additives such as tackifiers, oils, and/or plasticizers. The absence of these low molecular weight additives can have some desirable advantages, such as ... 

Pressure-sensitive adhesives (PSAs) based on acrylic, natural rubber and silicone are employed primarily for ease of application. To name Just a few applications, PSAs bond decals to surfaces, interior decorative surfaces to interior panels, interior trim pieces in place directly or hook and loop tape for the same purpose, structural shims in place during manufacturing and acoustic (sound deadening) materials to body skin interior surfaces. Tape products with pressure-sensitive adhesive on one or both surfaces are used for such functions as cargo compartment sealing, as a fluid barrier to prevent spills and leaks in the lavatories and... 

Today, even in the most developed countries, natural adhesives dominate the market because they are less expensive than synthetic-based materials, and they perform the intended function. Natural rubber is still the most widely used base material in pressure-sensitive adhesives. The first such modern uses were flypaper to trap flying insects, and medical bandages and tapes. Because of restrictions on the use of pesticides in many countries, both natural rubber and sticky synthetic materials have returned full circle to one of their original uses in trapping rodents and other small mammals. Natural rubber solvent solution adhesives are widely used throughout the world as general-purpose adhesives. 

Adhesives as materials can be classified in a number of ways such as chemical structure or functionality. In this book, adhesives have been classified into two main classes natural and synthetic. The natural group includes animal glue, casein- and protein-based adhesives, and natural rubber adhesives. The synthetic group has been further divided into two main groups industrial and special compounds. Industrial compounds include acrylics, epoxies, silicones, etc. An example of the specialty group is pressure-sensitive adhesives. 

Other adhesives such as hot melt adhesives (HMA), poly(vinyl acetate) (PVA, catalyzed or uncatalyzed), pressure-sensitive adhesives (PSA), or elastomeric adhesives (based on natural or synthetic rubbers) are also used in wood bonding (7). However, their use is mostly limited to nonstructural applications (eg, secondary manufacturing processes such as kitchen furniture, interior joinery, decorative paper, and packaging) where strength and water resistance are of limited concern. 

In general two types of adhesives are used for the manufacture of baby diapers, feminine-hygiene, and incontinence products. For simple construction purposes, hot-melt adhesives based on amorphous poly(alpha-olefins) (APAOs) are used. High-quality constructions are produced with adhesives based on styrenic block copolymers. For bonding of elastic materials such as polyurethane foam, lycra and natural rubber strands, and hydrophilic and hydrophobic of nonwovens, pressure-sensitive adhesives (PSAs) based on styrenic block copolymers are used. Hot-melt adhesives are the most common types of adhesive. The most widely used synthetic block copolymers are styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS), and styrene-ethylene-butadiene-styrene (SEES) with different styrene contents. 

The first pressure sensitive adhesives were based on natural rubber and rosin. They were applied as patches and tapes for surgical use [203], In the 19th century some early technical tapes were derived therefrom (e.g., Citoplast, P. Beiersdorf Co., Germany), but the application range was very narrow. When spray painting was introduced in the automotive industry, such tapes were employed to mask color lines. They were imperfect and had to be improved [204]. This was the starting point for the development of industrial tapes. 

Before the 1970s, the pressure sensitive industry was employing solvent-based systems made from SBR or natural rubber. About two decades ago, hot melt pressure sensitive adhesives based on styrenic block copolymers (mainly styrene-isoprene-styrene) and aciylic emulsions were introduced. The reason for these technological developments was to decrease the dependency on solvents. Today hot melts account for about 20% of the pressure sensitive adhesive volume, up from less than 10% in 1975. 

Formulation. Unlike the natural rubber pressure sensitive adhesives, acrylic adhesives are often supplied in a ready-to-use form. Natural rubber adhesives require time-consuming and costly mastication of the rubber followed by dissolving in solvent. In addition, they must be formulated with a tackifier resin and antioxidants, neither of which is required with an acrylic adhesive. The acrylic adhesives are known for their good UV and oxidative stability while the rubber-based adhesives, because of their chemical unsaturation, are poor in these properties. In general, tackifiers are not required with acrylic adhesives as tack can be designed into the polymer by the proper choice of... 

The process of masticating and dissolving natural rubber is important for pressure sensitive formulation as well as for solvent cement production. Pressure sensitive tapes and labels based on natural rubber are a significant part of the rapidly growing pressure sensitive adhesive... 

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